cleaning up some explicit signatures and fixing nullability lifecycle peeking

android/libraries/rib-android/src/main/kotlin/com/uber/rib/core/RibActivity.kt

@@ -37,6 +37,7 @@ import com.uber.rib.core.lifecycle.ActivityLifecycleEvent
 import com.uber.rib.core.lifecycle.ActivityLifecycleEvent.Companion.create
 import com.uber.rib.core.lifecycle.ActivityLifecycleEvent.Companion.createOnCreateEvent
 import io.reactivex.CompletableSource
+import io.reactivex.Observable
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.rx2.asObservable
@@ -50,17 +51,17 @@ abstract class RibActivity : CoreAppCompatActivity(), ActivityStarter, Lifecycle
   private val callbacksObservable = callbacksFlow.asObservable()
 
   /** @return an observable of this activity's lifecycle events. */
-  override fun lifecycle() = lifecycleObservable
+  override fun lifecycle(): Observable<ActivityLifecycleEvent> = lifecycleObservable
 
   /** @return an observable of this activity's lifecycle events. */
-  override fun callbacks() = callbacksObservable
+  override fun callbacks(): Observable<ActivityCallbackEvent> = callbacksObservable
 
   override fun correspondingEvents(): CorrespondingEventsFunction<ActivityLifecycleEvent> {
     return ACTIVITY_LIFECYCLE
   }
 
-  override fun peekLifecycle(): ActivityLifecycleEvent {
-    return lifecycleFlow.replayCache.last()
+  override fun peekLifecycle(): ActivityLifecycleEvent? {
+    return lifecycleFlow.replayCache.lastOrNull()
   }
 
   override fun requestScope(): CompletableSource {

android/libraries/rib-base/src/main/kotlin/com/uber/rib/core/Interactor.kt

@@ -23,6 +23,7 @@ import com.uber.autodispose.lifecycle.LifecycleScopeProvider
 import com.uber.autodispose.lifecycle.LifecycleScopes
 import com.uber.rib.core.lifecycle.InteractorEvent
 import io.reactivex.CompletableSource
+import io.reactivex.Observable
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.rx2.asObservable
@@ -55,7 +56,7 @@ abstract class Interactor<P : Any, R : Router<*>> : LifecycleScopeProvider<Inter
   }
 
   /** @return an observable of this controller's lifecycle events. */
-  override fun lifecycle() = lifecycleObservable
+  override fun lifecycle(): Observable<InteractorEvent> = lifecycleObservable
 
   /** @return true if the controller is attached, false if not. */
   override fun isAttached() = lifecycleFlow.replayCache.last() == InteractorEvent.ACTIVE
@@ -139,7 +140,7 @@ abstract class Interactor<P : Any, R : Router<*>> : LifecycleScopeProvider<Inter
   }
 
   override fun peekLifecycle(): InteractorEvent? {
-    return lifecycleFlow.replayCache.last()
+    return lifecycleFlow.replayCache.lastOrNull()
   }
 
   final override fun requestScope(): CompletableSource {

android/libraries/rib-base/src/main/kotlin/com/uber/rib/core/Presenter.kt

@@ -19,6 +19,7 @@ import androidx.annotation.CallSuper
 import com.uber.autodispose.ScopeProvider
 import com.uber.rib.core.lifecycle.PresenterEvent
 import io.reactivex.CompletableSource
+import io.reactivex.Observable
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.MutableSharedFlow
@@ -70,7 +71,7 @@ abstract class Presenter : ScopeProvider {
   }
 
   /** @return an observable of this controller's lifecycle events. */
-  open fun lifecycle() = lifecycleObservable
+  open fun lifecycle(): Observable<PresenterEvent> = lifecycleObservable
 
   override fun requestScope(): CompletableSource {
     return rxCompletable(Dispatchers.Unconfined) { lifecycleFlow.take(2).collect() }

android/libraries/rib-base/src/test/kotlin/com/uber/rib/core/InteractorAndRouterTest.kt

@@ -102,6 +102,7 @@ class InteractorAndRouterTest {
     }
     val router = TestRouterA(parentInteractor, component)
     val parentObserver = RecordingObserver<InteractorEvent>()
+    parentInteractor.lifecycle()
     parentInteractor.lifecycle().subscribe(parentObserver)
     router.dispatchAttach(null)
     Truth.assertThat(parentObserver.takeNext()).isEqualTo(InteractorEvent.ACTIVE)

android/libraries/rib-router-navigator/src/main/kotlin/com/uber/rib/core/RouterNavigatorEvents.kt

@@ -15,6 +15,7 @@
  */
 package com.uber.rib.core
 
+import io.reactivex.Observable
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.rx2.asObservable
@@ -25,7 +26,7 @@ class RouterNavigatorEvents private constructor() {
   private val _events = MutableSharedFlow<RouterNavigatorEvent>(0, 1, BufferOverflow.DROP_OLDEST)
 
   /** @return the stream which can be subcribed to listen for [RouterNavigatorEvent] */
-  val events = _events.asObservable()
+  val events: Observable<RouterNavigatorEvent> = _events.asObservable()
 
   /**
    * Emits a new [RouterNavigatorEvent] on the stream.